Electronic multiplier



June 9, 1953 A. H. DICKINSON ELECTRONIC MULTIPLIER l5 Sheets-Sheet 1 Filed June 18. 1949 a d S E B AGEN June 9, 1953 A. H. DICKINSON ELECTRONIC MULTIPLIER Filed June 18, 1949 FEJEL 15 Sheets-Sheet Z June 9, 1953 A. H. DICKINSON 2,641,

ELECTRONIC MULTIPLIER Filed June 18, 1949 15 Sheets-Sheet 5 BEA AGEN? i June 9, 1953 A. H. DICKINSON ELECTRONIC MULTIPLIER l5 Sheets-Sheet 4 Filed June 18, 1949 I, INVENTQR Arthur/1171;110:500

June 1953 A. H. DICKINSON 2,

ELECTRONIC MULTIPLIER Filed June 18, 1949 15 Sheet s-Sheet 5 INVENTOR Aft/ulfH. DI CK U150]! June 9, 1953 A. H. DICKINSON 2,641,407

ELECTRONIC MULTIPLIER Filed June 18, 1949 15 Sheets-Sheet 6 TEE-5d- INVEN TQR Arthur/i mmasm June 9, 1953 A. H. DICKINSON 2,641,407

mzcmomc uuwxpum Filed June 18, 1949 15 Sheets-Sheet 7 June 9, 1953 A. H. DICKINSON ELECTRONIC MULTIPLIER l5 Sheets-Sheet 9 Filed June 18. 1949 Q 3% Q Es INVENTOR A/t/ulf h. BIC/(M500 8W9 AGENT.

June 9, 1953 A. H. DICKINSON 2,641,407

ELECTRONIC MULTIPLIER Filed June 18, 1949 15 Sheets-Sheet 10 E 5% s t a:

June 9, 1953 A. H. DICKINSON 2,641,407

' ELECTRONIC MULTIPLIER Filed June 18 1949 15 Sheecg-Sheet 1s EAL INVENTOR Aft/Ill! H. DUI/ M8017 June 9, 1953 A. H. DICKINSON 2,641,407

ELECTRONIC MULTIPLIER Filed June 18, 1949 I 15 Sheets-Sheet 14 2' mun a June 1953 A. H. DICKINSON 2,641,407

ELECTRONIC MULTIPLIER Filed June 18, 1949 15 SheetsSheet 15 INVENTOR Aft/Ill! H. DlCMHSOI'I Patented June 9, 1953 s ELECTRONIC MULTIPLIER Arthur H. Dickinson, Greenwich, Conn, assignor to International Business Machines Corporation, New .York, N. Y., a1corporation of New York Application June 18, 1949, Serial No. 99,959

This invention relates and more particularly to such a multiplier wherein the product is obtained by over-and-ove rad dition without employing column shift.

7 One of the principal considerations in multiplier design has been the speed of the multiply ing operation. To effect an increase in this speed, column shift is employed to decrease the number of cycles of operation required to solve a given problem. Such is desirable in mechanical multipliers due to the inherent factors limiting their speed of operation. However, an

electronic multiplier operatesso fast thatvthe number of cycles of operation necessary to solve a given problem ceases to be a major consideration so far as its practical applications are conc'erned;

Accordingly, a principal object of this inventionis -to provide an improved electronic 'multiplier which does not employ column shift.

Another object is to provide a novel electronic multiplier wherein to obtain a product the multiplicand is entered into the result register a number of times equal to the multiplier.

Another object is to provide a novel multiplier sequentially operable in response to input entries t5 electronic multipliers;

19 Claims. (Cl; 235 61) further entries into the multiplicand receiving device, the result register and the multiplie'rrev-r.

ceiving device. I r

A further object is to provide a novel coincidence circuit responsive to produce an output upon the receipt of the third of three preselected. voltages and upon the removal of any one of said voltages thereafter.

A further object is to provide a novel multi plier interpreter circuit selectively responsive to a stable condition of the multiplier receiving deviceto permitv entriesinto the multiplicandre- 'ceivingdevice,

and having a single order multiplicand receiving device to accommodate a multiplicand having a plurality of orders. 1

A further object is to provide a novel circuit for effecting carry between the digit receiving input orders of the result register when no errtries are being received by those orders.

A further object is to provide an electronic multiplier having a novel multiplicand receiving device wherein the value of the multiplier de- 'termines the entry of pulses into the multiplivalue of the respective digits of the multiplicand. Another object is to provide a novel circuit arrangement to'permit the simultaneous entry of all digital values of the multiplicand into the result register during one cycle of the multipli cand receiving device.

Another object is to provide a novel circuit arrangement wherein a change in the stable condi- An ancillary object issto provide a circuit. which isfresponsive to pulses, when read out, pulses are not being made into the multiplicand receiving device, to effect a simultaneous switch ing of all the digit-representing elements thereof to a preselected'stable condition. 7 Another object is to provide an electronic mul-j tiplier wherein the pulse source used tovefiect' sequential operation of the multiplicand receiv-' ingdevice produces pulses at'least ten times as frequently as the occurrence of the pulses used to initiate that sequential operation. V

A still further object is to provide a, novel cir-v cuit arrangement including a trigger switchable to one stable conditionin response to a pulse from one source so that it permits entries to be made into thelmultiplicand receiving device and switchable to' its otherstable, condition in response toa pulse from another source only when the multiplicand receiving device has completed, a cycle ofoperation, 'A' still further object is to provide a novel circuit arrangement permitting the'entry of a num-'- ber of pulses equal to one less than the value of each digit, other than zero, of the multiplicand into each corresponding'order of the result reg. ister when'the multiplicand receiving device is' being sequentially operated and permitting only one additional entry to be made simultaneously into each such order of the result registensaid entries also being. made prior to the switching of the digit-representing elements of the multipulses, multiplicand and multiplier receiving de-Q vices and a result register inter-connected in a novel manner to perform themultiplication of two numbers representing a multiplicand and a tion of one digit-representing element of the multiplier receiving device is utilized to prevent multiplier, respectively. The multiplicand and multiplier are entered into their respective receiving devices by depressing the proper pusha button switches thereof and their product is displayed by the result register. The novel multiplicand receiving device uses a single series of nine digit-representing elements to accommodate a multiplicand having a plurality of digital orders.

The closing of a calculate switch conditions the entire multiplier to start multiplication of the entered numbers in response to the source of pulses. A .novel multiplier interpreter circuit is provided to respond to the multiplier receiving device to'eifect the operation of a trigger when the multiplier receiving device has received. a 7

number of pulses equal to the one-thousands complement of the particular multiplier used.v When the stable condition of the trigger is switched it causes an electronic gate control circuit to be energized to permit read out pulses 'to E be entered into themultiplicand receiving device to effect a sequential switching of the digitrepresenting elements thereof.

When the multiplicand receiving device -.re

'ceives a number of entries equal to the tens complement of the multiplicand digit Of' the lowest order and the nines complement of each higher order thereof an electronic gate is opened to permit entries into the corresponding order of the result register. When the multiplicand receiving device completes its sequential swiching' it biases the electronic gate controlling trigger so that the trigger is subsequently returned to its original condition. Simultaneously with this re.- turn another entry is made into each order of the result register corresponding to the orders of illustrated in the accompanying drawings, which.

disclose,'by way of example, the principle of the invention and the best mode, which has been contemplate, of applying that principle.

In the drawings:

Fig. 1 is a block diagram illustrating one embodiment of the multiplier of'the invention.

Fig. 2 is a circuit diagram of a trigger circuit typical of those employed by the invention.

Fig. 2a is a diagrammatic showing of the trigger circuit of Fig. 2.

Fig. 3 shows the relative arrangement of subsequent figures to realize the complete circuitv diagramof the multiplier.

Figs. 3a, 3b, 3c, 3d, and 3e taken together comprise a circuit diagram. of the multiplier.

Fig. 4 shows the relative arrangement of subsequent figures to realize a timing chart representative of the operation of the multiplier in'performing a specified problem; and

Figs. icy lb, 4c, 4d, 4e, 4f, 49, and 4h taken together represent a timing chart showing the operation of a multiplier when the solution of a specified problem is accomplished.

Various electronic circuits, each employing one tube, are employed by the invention. When the electrode potentials of the tubes are at certain predetermined values, these tubes respond to an 4 input pulse to momentarily change their conductive state and usually to effect some other operation. When the electrode potentials are at certain other values the tubes will not respond to an input pulse. Such circuits are referred to herein as gates and the tubes employed in the circuits are. referred to as. gate tubes. .'When. such a tube will-not respond to its usual input pulse it is referred to as dc-conditioned and when it will respond to that input itis referred to as conditioned. 1

A number of trigger circuits are employed having two tubes, oneconductive and the other non-conductive and. vice versa to represent two stable conditions. These two conditions are referred to hereinas the Left and Right condition. "Left condition means that the left-hand tube of the trigger is conductive and that the righthand tube is non-conductive. Right condition means that the right-hand tube of the trigger is conductive andthat the left-hand tube is nonconductive. V

To facilitate the description the specification Portions of the multiplier which do not have a designated part therefor are described in connection with the designatedpart deemed most pertinent.

General description The general scheme of the invention will now be explained with reference to the block diagram of Fig. 1.. r

To effect multiplication the multiplicand is entered in the result. register a number oftimes;

equal to the multiplier. The speed of the actual. multiplication is determined by the frequency of the pulses used to effect it which pulses may be of a fixed frequency or may occur at random.

The pulses used to effect operation are derived from an oscillator Ill and av circuit network ll actuated by the oscillator 10. The oscillator l0 produces two distinct series of positive and negative pulses. The pulses of one series are referred to as E pulses and the pulses of the other series are referred to as F pulses. The positive E pulses are one-hundred-and-eighty degrees out of phase with the negative E pulses and in phase with the negative F pulses. -Accordingly, the positive F pulses are one-hundred-and-eighty degrees out of phase with the negative F pulses and in phase with the negative E pulses. The E pulses appear on a lead IOE and the F pulses appear one lead 10F. I

The-F pulses are transferred overv the lead 10F to actuate circuit network II to cause'it to produce two distinct. series of positive and negative pulses. The pulses of one series are referredto;

as C pulses and the pulses of the other series are referred to as D pulses. The positive C pulses are one-hundred-and-eighty degrees :out of phase with the negative C pulses and in phase with the negative D pulses. Accordingly, the positive D pulses are one-hundred-and-eighty degrees out ofphase with the negative D'pulse's and in phase with the negative C pulses. One C pulse and one D pulse. occur for: each sixteenth able to produce an output for'each order of themultiplicand in. response to the condition of the associated push-button switches provided to accommodate a multiplicand of three orders. The

multiplier. receiving device Mp comprises a separate order for each order of the multiplier, there being shown the orders MpU, MpT, and MpI-I corresponding respectively to the units, tens, and

hundreds digit of the multiplier. The particular correct push-button switch associated therewith.

The result register RR comprises six orders labeled RRU, RRT, HRH, RRTh, RRTTh, and RRHTh to designate the units tens, hundreds, thousands, ten-thousands, and hundred-thousands orders, respectively. Epulses are continuously transferred over the leads HIE and I2 to the units order RRU and over the leads IOE, l2 and 13 to the tens order RRT. The six orders of the result register are provided to accommodate the. product of a three-digit multiplicand and a three-digit multiplier as provided for in the multiplicand and multiplier receiving devices.

The buffer stage I4 is energizedover a lead l5 from the units order RRU of the result register and the output of the, buffer stage-is transferred over a lead IE to the tens order RRT to effect carry thereto after each tenth pulse is applied to RRU. The buffer stage I4 provides a delay in transferring the pulse from RRU to RRT so that the carry pulse will not be applied to RRT at the same time it receives its normal input pulse. When RRU produces an output pulse in response to each tenth input pulse it does not change the conductive condition of the buffer stage I4 because that pulse is of the wrong polarity to effect such a change. pulse transferred over line I2 to RRU causes a positive pulse to be transferred over the lead to the buffer stage from RRU and the buffer stage then transfers a negative carry pulse to R-RT to advance it by a count of one.

The buffer stage I! is energized over the lead I8 from the tens order RRT of the result regis-' ter and the output of the buffer stage is transferred over a lead 19 to the hundreds order RRH to effect carry thereto. The buffer stage I? functions in exactly the same manner as does buffer stage l4.

Carry between RRH and RRTh, RRTh and RRTTh, and RRTTh and RRHTh is conveyed over the leads 2|, 2 l, and 22, respectively. Nodelay in the application of these carry-pulses is necessary because the carry pulsescon'stitute' the sole input to these orders.

The multiplicand is entered into the result reg ister a number of times equal to the value of the multiplier, the multiplicand being entered in the units, tens, and hundreds order of the result register in accumulator fashion. This is to say that the units, tens, and hundreds order respectively of the result register receive simultaneouslya number of pulses equal to the units, tens, and

hundreds digital values of the multiplicand dur-- The output of the gate 24 is transferred to RRT over lead l6 and the output of gate 25 is transferred to RRH over lead !9. The multiplicand receiving device controls the entry of pulsesinto the result register by effecting selective transfer of voltage over the leads 32, and 34 to condition gates 23, 24 and 25, respectively, to respond to positive Epulses.

However, the next negative E The gate 35, normally conditioned. is co'ntin uously supplied over a line 31 with positive F pulses from line 10F. These pulses render. gate t5 momentarily'conductive and negative pulses are transferred over lead 38 to the. multiplicand receiving device Me. However, these pulses have no effect upon Me unless it is not in its initial stable condition whereupon a single pulse switches it to its initial stable condition. The gate 36, normally de-conditioned, is continuously supplied over a lead 40 with negative E pulses from the lead IUE. These pulses have no effect on gate 36 until it is conditioned and then allow it to effect pulse transfer .over leads 39 and 38 to the multiplicand receiving device. Whether pulses transferred from gate 36 will effect the stable condition of the multiplicand receiving device depends upon the bias applied to the device over a lead 4 l;

The conditioning of gates 35 and 36 is controlled by the trigger Tmc which isnormally in the Left condition. When the trigger Tmc is switched to the Right condition, gate 35 is deconditioned by the voltage applied to it over lead 42. At the same time a voltage is applied over a lead 4| to the multiplicand receiving device to render it responsive to pulses from the gate 36 and a voltage is applied over lead 43 to the gate' 36 to condition it.

After the multiplicand receiving device has completed its cycle of operation, a bias is applied over the lead 44 to the trigger Tmc which permits the trigger to be switched Leftby the next negative F pulse applied to it over lead HIF. v

The multiplier interpreter 41;,triggers 48 and 49, calculate switch 50, and gate 5| comprise all the remaining blocks shown in Fig.1,

Calculate switch 50 is operated to condition the system for operation and thereupon a pulseis transferred over a lead 52 to switchtrigger 49 to the Right condition. At the same time a pulse is transferred over leads 52 and 53 to Mpl-l to change the conductive condition of one of the digit-representing elements thereof. When another one of the digit-representing elements of MpH switches to one conductive condition, it

causes a pulse to be transferred over leads 54 and. 55 to the trigger 49 to switch it to the Left condition. At the same time, a pulse is transferred over leads 54 and 56 to the trigger 48, to'

switch it to the Left condition.

Trigger 49 is connected via a lead 51 to the gate 5| so that, when trigger 49 is switched to the Right condition gate 5| is conditioned and when trigger 49 isswitchedto the Left condition gate 5| is de-conditioned' After gate 5| is conditioned it is rendered conductive in response to the next positive D pulse appearing on the line IID and thereupon gate 51 transfers a negative pulse over a lead 58 to MpU.

When trigger 48 is switched to the Right condition, as described hereinafter, a potential is transferred therefrom over a lead 59 to condi-- has been sequentially cycled a pulse is transferred over a lead 64 to Mp-T and over the leads 64 and to one digit-representing element of MpU. Similarly a pulse is transferred from 7 MpT over a lead 66 to MpI-I and over theleads 66 and 8?. to one digit-representing element of Each of the circuits of the multiplier interpreter 41 includes a grid-controlled tube. The circuits are inter-connected so that, when the tubes of circuits [i and 52 are conductive, the

tubes of buffer circuits 8i and 53 are non-conductive, Also,.when the tubes of circuits 6!} and B'Zare non-conductive, the tubes of buffer circuits BI and 53 are conductive. The latter is the normal condition of the circuits. A control electrode of the tube of circuit 62 is connected through a lead 68 to one side of digit-representing push-button switches (Fig. 30), associated with the units order MpU of the multiplier receiving device Mp. A control electrode of the tube of circuit 60 is connected through a lead as to one side of digit-representing push-button switches (Fig. 30) associated with the tens order MpT of the multiplier receiving device Mp. A

fective to change the condition of the trigger because it is already in the Left condition. However, the next pulse applied to the multiplier receiving device Mp causes the tube of circuit 53 to become conductive. A negative pulse transferred over the lead H switches trigger is to the Right condition to cause the entry of the multiplicand into the result register in the manner set forth above. The trigger 43 is switched back to the Left condition in response to a pulse transferred to it over the leads 56 and 56 from MpI-I when the thousands pulse is applied to the multiplierreceiving device Mp. Also a pulse is trans-,

Fig. 2' shows a trigger T typical of the type employed in the invention. The trigger is shown as comprising a tube of the type having two'triode tube sections with a common cathode in a single envelope. designated L and the right-hand tube section is designated R. These sections are referred to herein as the tube L and tube R, respectively.

The tubes L and R are alternately conductive and non-conductive and vice versa. As stated hereinbefore, when the tube L is conductive the trigger is referred to as being in the Left condition, and when the tube R is conductive the trigger is referred to as being in the Right condition.

The common cathode of the tubes L and R is connected to ground line 12g. The plate of the tube L is connected through a resistor l3 to the high voltage line 1 th and the plate of the tube R is connected through a resistor 15 to the line 14h. A lead 16 connects the plate of the tube R to the junction of resistor 75 and a voltage divider consisting of resistors 11 and T8 in series, the introtion of the resistors 17 and IS-being connected to the control grid of the tube L. The lower end The left-hand tube section is of resistor H3 is connected to cancel bias-line CBL and a capacitor 19 is connected in parallel with the resistor "H. Similarly, a lead connects the plate of the tube L to the junction-of resistor i3 and a voltage divider consisting of resistors SI and 82 in series, the junction of resisters 8! and 82 being conected to the control grid of the tube R. The lower end of resistor 82 of this divider is connected to a bias-voltage line 8322. the resistor 8 I. The'bias-voltage line 83b and the cancel-bias line CBL are connected together through cancel-bias switch CBS.

Switch CBS provides for quick resetting of the trigger to its initial stable condition. As'shown, this initial condition is the Left condition. However, the connection of the lower end of resistor 82 to line CBL and the connection of the lower end of resistor 18 to the bias-voltage line 331) will cause the Right condition to be the initial condition.

As used herein, 'if'the Left condition is the initial condition an x is placed to the lower left of the tube L, and if the Right condition is the initial condition an a: is placed to the lower right of the tube R.

When switch CBS is opened, the grid-bias voltage applied to the tube L rises above the cutoff bias and this tube is rendered conductive irrespective of its condition immediately prior to the time when the switch was opened to disconnect line CBL from line 83b. The closing of switch CBS does not remove the positive bias voltage onthe tube L but permits it to remain conductive so that the trigger is placed in the Left condition.

The actual voltage at the control grid of the tube L is determined, among other things, by the volt-' age divider action of resistors '55, El, and i8.

Asingle cancel-bias switch CBS is used to reset all of the triggers employed herein to their initial condition.

Terminal I is connected to the control grids of the tubes L and R through capacitors and 86, respectively. The application to the terminal I of either positive or negative pulses of appropriate amplitude and duration will effect a change in the stable condition of the trigger circuit.

Since the trigger circuit employed is well known in the art, one cycle of its operation in response to negative pulses applied to terminal I will bedescribed briefly. A similar cycle may be eifected by the application of positive pulses.

When the first negative pulse is applied tothe terminal I it is transferred to the control grids of the tubes L and, R through the capacitors 85 and 86, respectively. This pulse has no direct effect on the tube R because its control grid is,

already biased below cutoif. However, this negative pulse decreases the bias on the control grid of the tube L and its plate voltage rises rapidly. This rising voltage is transferred from the plate of tube L through lead 8B and the parallel connected resistor 8| and capacitor 84 to the control grid of the tube R. The grid of tube R is thus made sufficiently positive to start conduction through that tube. The resulting decrease of the voltage atthe plate of the tube R is transferred over the lead 15 and the parallel-connected resistor 1! and capacitor 19 to the control grid of the tube L' to effect a further increase of the voltage at its plate. again transferred to the control grid of the tube R to render it still more conductive. The resulting decreased voltage at the plate of the tube R is again transferred to the control grid of the tube A capacitorfi l is connected in parallel with This increased voltage is L to render it still less conductive. This cumulaapplied to the input terminal I decreases thevoltage at the plate of the conducting tube R. This voltage is transferred to the control grid of the tube L to permit that tube to become conductive. The resulting decreased voltage at the plate of the tube L is transferred to the control grid of the tube R. to render it still more conductive. the tube R is transferred to the control grid of the tube L to render it still less conductive. This cumulative action is continued until the tube R is rendered non-conductive and the tube L is rendered uniformly conductive to place the trigger in the Left condition.

While it has been explained that the trigger is switched from either stable condition to the other by the application of pulses to the terminal I,

and hence to the grids of the tubes L and R simultaneously, it is understood that the trigger may be switched from one stable condition to the other by the application of a pulse to the control grid of only one tube or by any other conventional means such as plate or cathode keying.

In the schematic showing of Fig. 2a the trigger is designated as T as in Fig. 2. The terminals shown in Fig. 2a correspond to the similarly designated terminals shown in Fig. 2. It should I be noted that the absence of a connection to the terminal I in a schematic showing such as Fig. 2a indicates that capacitors 85 and 86 shown in Fig. 2 are omitted. A connection to the terminal I indicates that the trigger is switched from either stable condition to the other by the simultaneous- The following description is best understood by arranging the drawings as illustrated by Fig. 3.

The oscillator l9 (Fig. 3b) includes dual type tube 96 having two triode sections referred to hereinafter as 90L and 90R. The common cathode of tubes 90L and90R are connected to ground line 129 and the plates are connected through their respective. resistors 92 to the high-voltage line 14h. The control grid of each tube is connected through a bias resistor 93 to line 12g and the grid of each tube is connected to-the plate of the other through a capacitor 94. It is seen that these tubes are connected as a conventional multivibrator. Such a multivibrator is well known in the art-and it suffices to state that the tubes 90L and 9BR are alternately conductive and non-conductive and vice versa because of small differences in the characteristics of those tubes and the components used. This operation is continuous and causes positive and negative pulses to be produced at the plates of the tubes- 9BL and 90R. When the voltage at the plate of 99L is low the voltage at the plate of 90R is high and v ice versa. Hence, .the.. voltage pulses The decreased voltage at the plate of at these plates are alternately positive and negative and 180 out of phase.

The plate-of the tube L is connected through a capacitor to the control grid of amplifier tube 96E. The cathode of 96E is connected directly to line 129 and its plate connected through a resistor 91 to the line 14h. The control grid of tube 96E is connected through a bias resistor 98 to the line 12g. This amplifier may be of any "suitable conventional design and serves only to amplifiy the pulses appearing at the plate of tube 90L. The pulsesappearing at the plate of amplifier tube 96E are referred to herein as E pulses and are transferred over the line IDE.

A similar amplifier tube 96F is .providedto amplify the voltage pulses appearing at the plate of the tube. 90R. These pulses are transferred from the plate of tube 96F, over line IUF to the circuit network II and to other circuits referred to hereinafter. The circuit network H has '4 triggers designated Tl, T2, T4, and T8 connected in series chain to operate in binary fashion.

When in the starting or initial condition, of the triggers Tl, T2, T4,.and T8 is connected to be in the Left condition. Positive and negative F pulses are applied from the line IUF to the terminal I'of trigger Tl. However, trigger Tl, as the remaining triggers, is responsive only to negative F pulses so that positive F pulses have no effect on the stable condition of the circuit. Terminal prL in the plate resistor of the left tube of trigger TI is connected over a line 99 to the terminal I of trigger T2 so that whentrigger TI is. switched to the Left condition a negative pulse is transferred over .lead 99 to the control grids of both tubes of the trigger T2 to effect a change in the stable condition of the trigger T2. In a like manner, trigger T2 is connected to trigger T4 and trigger T4 is connected to trigger T8. The operation of these triggers may be understood by reference to Table I below.

TABLE 1 Czrcuzt network 11 Triggers Input Pulse (-F) 0 L L L L 1 R L L L 2 L R L L 3 R R L L 4 L L R L 5 R L R L 6 L R R L 1 R R R L s. L L L R R L L R L R L R R R L R r L L R R R L R R L R R R R R R R L L L L It is seen that the first input pulse (F) applied to the terminal I of the trigger Tl causes that trigger to switch to the Right condition. As

a result, a positive pulse is transferred over the line 99 to trigger T2 but does not effect the stable condition of T2 because, as stated, it is non- .input'pul'se switches the trigger TI to the Right 

